(Newser)
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Transplanting healthy cells into the brains of people with Parkinson's alleviates symptoms, but sufferers showed signs of deterioration as the disease spread to the grafted cells, according to two studies in the journal Nature Medicine. Scientists in Sweden and Chicago discovered similar results in patients who received cell transplants up to 16 years ago.

The findings are a blow to hopes of finding permanent relief for those with the debilitating disease. The results contradict the more positive conclusions of another study and will likely reignite the debate over using stem cells in the future for similar grafts. "Grafted cells can be affected by the disease," wrote the Chicago researchers. "It's unclear whether a similar fate would befall stem cell grafts."